1. Field of the Invention
The invention pertains to silicone defoamer compositions containing organopolysiloxane-crosslinked arylalkyl-group-containing T and Q siloxy units.
2. Description of the Related Art
Many aqueous systems foam excessively under agitation, and are thus in need of foam control agents to control the amount of foam generated. The aqueous systems may be of natural or synthetic origin, particularly the latter. Examples include surfactant-laden emulsions from oil and gas recovery, and the so-called “black liquor” from the processing of cellulosic and lignocellulosic fiber-containing materials into paper products. Additional examples include, in particular, aqueous washing compositions for use in laundering and machine dishwashing. While most hand dishwashing compositions are designed to be high foaming to generate a perception of high cleaning activity, the generation of foam in clothes washers and machine dishwashers is known to interfere with cleaning ability. Moreover, excessive foaming can impose a much greater load on the electrical motor driving such devices, to the point of thermal destruction of the motor. The foam additionally presents the possibility of overflow and thus water damage to surrounding areas.
To mitigate these undesirable effects, surfactants used in machine laundering and dishwashing and other fields, have often been of the low foaming type. Unfortunately, cleaning efficiency is frequently compromised by their use. In addition, other ingredients in detergent formulations, for which there are no low foaming substitutes available, may also produce foam.
Thus, in fields where high cleaning efficiency and/or low foam generation is necessary, defoamers have been added to reduce the amount of foam generated and/or to achieve rapid collapse of foam. For this purpose, a wide variety of materials have been proposed over the decades as defoamers. Early on, products such as mineral oils, high boiling petroleum fractions and long-chain alkyl industrial products such as tall oil acids and oxo alcohols have been used. Silicone fluids, particularly polydimethylsiloxanes, have also been used. Most of these materials continue to be used today. However, in many cases, their defoaming activity is too low, or other problems, such as objectionable odor, prevent their use.
Moreover, some defoamers have proven acceptable in some defoaming applications, but not in others. Black liquor, for example, presents a harsh environment which can cause defoamers to decompose and lose their effectiveness, while laundry detergent compositions often contain very high levels of surfactants, and highly alkaline substances, which render many defoamers ineffective.
WO 03/089108 discloses particulate foam control agents containing 1-30 parts by weight of a silicone antifoam, 45-99 parts particulate carrier, 2-50 parts of fluorescent whitening agent, and 1-40 parts binder. The silicone antifoams are conventional linear or branched silicones terminated by trimethylsilyl groups, as disclosed in EP-A-578424. Other silicone antifoams are stated to be disclosed in GB 639673, EP 31532, EP 217501, EP 273,448, DE 38 05 661, GB 2,257,709, and EP-A-1,075,864.
U.S. Pat. No. 6,521,587 B1 attests to the long sought need for defoamers in heavy duty detergent formulations, and proposes use of defoamers containing chain-pendent alkylphenyl-substituted poly(ethyl, methyl)siloxanes; a water-insoluble hydrocarbonoxy oil such as mineral oil, vegetable oil, or insoluble hydrocarbon alcohols, carboxylic acids, or esters; an organosilicon resin, and a hydrophobic filler, the foam control agent being free of polydimethylsiloxanes or containing less than 20 wt. % polydimethylsiloxane based on the weight of the alkylphenyl-substituted organopolysiloxane.
U.S. Pat. No. 8,536,109 B2 discusses the long sought need for efficient defoamers in liquid detergent formulations for laundering, and proposes a mixture of chain-pendent alkaryl-substituted organopolysiloxanes of the same type as in U.S. Pat. No. 6,521,587 B1 together with a silicone “resin” (which non-conventionally also includes linear silicone fluids) as a silicone defoamer, a hydrophobic filler, and a further polyether group-containing silicone resin containing both T and Q units.
WO 2013/167430 A1 discloses the continued need for efficient defoamers, and proposes the use of alkylene-linked organopolysiloxanes, fillers, organopolysiloxane resins, and optionally cyclic organopolysiloxanes, in heavily surfactant-loaded detergent formulations. The preparation of the defoamers starts with the cohydrolysis of vinyl-and hydrido-functional silanes, and generates considerable amounts of byproducts.
U.S. Pat. No. 6,521,586 B1 is similar in disclosure to U.S. Pat. No. 6,521,587 B1, and discloses similar ingredients, but does not require a water-insoluble non-silicon-containing organic fluids.
U.S. Pat. No. 8,084,566 B2 discloses long lasting defoamers which are produced by hydrosilylating an Si—H functional organopolysiloxane with an allyl ether-terminated organopolysiloxane, followed by reaction with a diisocyanate to produce urethane-linked composite polyether/silicone compounds, and which also contain a silicone resin.
U.S. Pat. No. 8,222,303 B2 discloses defoamer compositions containing an organopolysiloxane defoamer, hydrophilic silica, and a polyethersilicone. The defoamers are particularly useful in defoaming black liquor.
U.S. Pat. No. 8,461,221 discloses pulverulent antifoam particles comprising a silicone antifoam absorbed into a porous copolymer of urea, melamine, or a mixture of urea and melamine. The defoamers are said to be particularly useful in laundry detergent formulations.
There has been a continuing long sought need to provide defoamer compositions where one or more of the principal defoamers are easily synthesized, which provide high defoaming activity, and whose structure can be tailored for the particular end use desired.